Years ago, an immoral scientist with incredible luck to match his incredible genius rediscovered the blue spider lily, and the formula to resurrect demons. The new Demon King plotted his vile machinations with the utmost patience and caution, beginning to create new demons in 1975. However, starting in 1980, select families of great ability began to receive records of the Breathing Styles of antiquity. The Demon Slayer Corps was reborn, led by the heirs of the Ubuyashiki clan. They searched for new Demon Slayers for 15 years, training and directing them as they grew in strength from the shadows.

Then, in 1990, the Demon King changed the game by sending a broadcast worldwide. His demonic forces launched a simultaneous strike against every military installation across Japan and in the waters around the island nation, destroying any hope of an armed response. He informed the entire world that he held Japan under his rule, and was able to launch an uncontrollable plague on the rest of the world at any time if they interfered. Five years have passed since then, and a never-ending storm has surrounded Japan ever since, blocking any ships or planes attempting to leave or enter.

The Demon King's public declaration was for Japan to return to being an isolationist nation. Without the ability to counterattack, life has returned to some form of normalcy inside the island nation. However, the Demon King's horde of demons still roam the nation, hunting for their victims wherever they see fit. The Demon King's true purposes are unknown, and his influence on the Japanese government has made sure the Demon Slayers are in this fight alone.

Now it's your turn. Will you join the fight?